This invention relates generally to a means for testing an amplifier system having a plurality of amplifier modules, and more particularly to an arrangement with a test set for testing an automatic flight control system amplifier.
The avionics of modern aircraft and spacecraft may include an automatic flight control system having various input controls and sensors, an electrical system for integrating and amplifying signals from the controls and sensors, and output servo devices for controlling the craft.
The H-53 helicopter for example has an automatic flight control system (AFCS) which includes an AFCS amplifier having several amplifier modules. These include two identical pitch modules for redundancy, two identical roll modules for redundancy, an altitude module, a yaw module, and a yaw synchronizer module. An additional feature of the system provides hover control, which includes an altitude integrator module in the AFCS amplifier. Each module is one printed circuit card assembly. The seven or eight modules are inserted parallel to each other in jacks of the main chassis, on a multilayer flexible printed wiring board. There are also some components mounted directly on the chassis.
The established procedures for testing this amplifier in the past (used for many years) consisted of removing the seven or eight circuit-card modules and testing them individually on a component tester. There was no provision for electrically testing the amplifier chassis or comparing the response of different channels to a given input. One difficulty by way of example was that adjustment of certain parameters of individual modules might be within prescribed limits, but when used in the system be out of balance.